Hitherto, it has been known to use, as an asymmetric catalyst, a complex comprising a transition metal atom and an organic ligand as its constituents. It has also been known to select an optically active compound as the organic ligand, in particular an axially-asymmetric diphosphine ligand compound. However, the axially-asymmetric diphosphine ligand compound is very expensive in many cases. Thus, the compound is disadvantageous for industrial use.
Consequently, if there is any way an achiral ligand can be used instead of the axially-asymmetric diphosphine ligand compound, the method can be an advantageous method by which an optically active compound can be obtained at low costs.
As an example of asymmetric hydrogenation using such an achiral diphosphine ligand, there is a report wherein 2,2′-bis(diarylphosphino)-1,1′-biphenyl is used (see Non-patent Document 1). This describes an example of asymmetric hydrogenation using a diphosphine-ruthenium-optically active diamine complex. However, the asymmetric yield of the diphosphine-ruthenium-optically active diamine complex described therein is not very high in certain kinds of ketone used as the starting material thereof. The yield does not reach a practical level in some cases.
Non-patent Document 1: K. Mikami et al., Angew, Chem. Int. Ed., vol. 38, 495 (1999).